Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Segmentation fault when I pass a char pointer to a function in C.
Top Forums Programming Segmentation fault when I pass a char pointer to a function in C. Post 303016290 by dryden on Tuesday 24th of April 2018 02:25:18 AM
Old 04-24-2018
Quote:
Originally Posted by Corona688
It's implicitly a pointer, implemented as one internally, but the same way you're not allowed to change a string's contents, you're not allowed to change its value. Hardcoded.
Those... aren't really similar things. The array's address (the name) is only known at compile time, or debug info, but in the compiled code the 'name' is effaced and you're simply dealing with addresses hardcoded into the code.

Thus, there isn't really anything you can modify unless you were to write the code segment.

The string, I guess it could also be located in a code segment, but more likely is that they are actual data values in a read-only data segment.

As such, the array is not really a pointer, there is no variable anywhere holding its address. So, it's no different from not being able to change the address of some int value that you have defined.

When you do

Code:
char arr[20]; char *p = arr;

That's technically no different from

Code:
int i; int *q = &i;

But I find the biggest annoyance(?) of arrays and structs to be that you can only initialize them at declaration?
 

10 More Discussions You Might Find Interesting

1. AIX

Segmentation fault

I am tring to install Lotus Domino/Notes 5.0.5 on a AIX 4.3.3 server. I go to run the cdrom/ibmpow/install and I get the following error. Lotus Notes for Unix Install Program --------------------------------------------- ./install: 10088 Segmentation fault This had Lotus Notes installed... (1 Reply)
Discussion started by: jshaulis
1 Replies

2. Programming

Adding a single char to a char pointer.

Hello, I'm trying to write a method which will return the extension of a file given the file's name, e.g. test.txt should return txt. I'm using C so am limited to char pointers and arrays. Here is the code as I have it: char* getext(char *file) { char *extension; int i, j;... (5 Replies)
Discussion started by: pallak7
5 Replies

3. Programming

segmentation fault

If I do this. Assume struct life { char *nolife; } struct life **life; // malloc initialization & everything if(life->nolife == 0) Would I get error at life->nolife if it is equal to 0. wrong accession? (3 Replies)
Discussion started by: joey
3 Replies

4. Programming

pass a pointer-to-pointer, or return a pointer?

If one wants to get a start address of a array or a string or a block of memory via a function, there are at least two methods to achieve it: (1) one is to pass a pointer-to-pointer parameter, like: int my_malloc(int size, char **pmem) { *pmem=(char *)malloc(size); if(*pmem==NULL)... (11 Replies)
Discussion started by: aaronwong
11 Replies

5. Programming

segmentation fault in fwrite function

Hi, my code is written in proC and it is in UNIX(AIX).I have written a small code for writing data into a binary file,but while writing my program is giving core dump. Here Is my code---- fpWriteFile = fopen(WriteFileName,"wb+"); CHAR *recvgen; recvgen = (char... (7 Replies)
Discussion started by: ajaysahoo
7 Replies

6. Programming

C++ segmentation fault while checking for null pointer

void disptree(node *ptr) { if ((ptr->left) !=NULL) disptree(ptr->left); cout<<"Position:"<<ptr->pos<<" Data:"<<ptr->data<<endl; if ((ptr->right)!=NULL; disptree(ptr->right); } i'm getting a segmentation fault at the red line. i cannot understand what's the problem.... (3 Replies)
Discussion started by: vijaymrt
3 Replies

7. Programming

segmentation fault while returning from function.

I am working on the application in which I have to fetch values from the database and paste in url and send it to portal. table=get_result("SELECT serialno,cas,Mode,FLC,TLC,location,CompName,CompCode,FG,FC,DispNo,TruckNo,LWbill,RRGPN,INVNO,DCN,RQTY,DQTY,SQTY,DDATE,RDATE,SDATE,TTIME FROM... (1 Reply)
Discussion started by: er.rohan88
1 Replies

8. Programming

Using gdb, ignore beginning segmentation fault until reproduce environment segmentation fault

I use a binary name (ie polo) it gets some parameter , so for debugging normally i do this : i wrote script for watchdog my app (polo) and check every second if it's not running then start it , the problem is , if my app , remain in state of segmentation fault for a while (ie 15 ... (6 Replies)
Discussion started by: pooyair
6 Replies

9. Shell Programming and Scripting

Segmentation fault in function call, shell script

I am getting Segmentation fault at below function call in my script: get_x() { sqlplus -s / <<end | grep KEEP | sed 's/KEEP//;s///g' select 'KEEP' ,table_name from all_synonyms where upper(synonym_name)= '$1'; exit end x=$(get_x $1) echo " SQL OUTPUT IS :: $x" } I am getting output of... (1 Reply)
Discussion started by: IB_88
1 Replies

10. Programming

C. To segmentation fault or not to segmentation fault, that is the question.

Oddities with gcc, 2.95.3 for the AMIGA and 4.2.1 for MY current OSX 10.14.1... I am creating a basic calculator for the AMIGA ADE *NIX emulator in C as it does not have one. Below are two very condensed snippets of which I have added the results inside the each code section. IMPORTANT!... (11 Replies)
Discussion started by: wisecracker
11 Replies

LEARN ABOUT OSF1

uac

uac(1)							      General Commands Manual							    uac(1)

NAME

       uac - Unaligned Access Message Control

SYNOPSIS

       uac p | s [value]

       uac p | s [keyword]

OPTIONS

       The  following  options	are used with the uac command: Sets or displays the current option setting for the parent process Sets or displays
       the current option setting for the system

       The following keywords are used with the p option: Reset the current option settings to the default for the parent process Do not print the
       unaligned  access  warning message for the parent process Do not fix the unaligned access for the parent process Deliver a SIGBUS signal to
       the parent process

       The following keywords are used with the s option: Reset the current option settings to the  default  for  the  system  Do  not	print  the
       unaligned access warning message for the system

       Usually, the parent process is the shell.

DESCRIPTION

       Most  complex  instruction set computers (CISC) can access unaligned data but only at a significantly reduced speed.  Most reduced instruc-
       tion set computers (RISC) do not attempt to handle unaligned accesses.  Instead, they generate an unaligned access trap and let the operat-
       ing system handle the fault.

       The  default  action for the operating system when an unaligned access fault occurs is to fix the unaligned access fault and then display a
       warning message informing the user process that an unaligned access fault has occurred.	 The  warning  message	has  the  following  form:
       "Unaligned  access  pid=nnn  <prog_name> va=virtual_addr pc=pc_addr". If you want to change the code to prevent the unaligned access faults
       from occurring in the future, the warning message gives you the information you need to locate the code causing a fault. (See the  Program-
       mer's Guide for details on the causes and effects of misaligned data.)

       In  addition,  the default action for the operating system is to not deliver a SIGBUS signal to the parent process when an unaligned access
       fault occurs.

       These defaults are satisfactory for most users, but some users require a different behavior and want to specify their own Unaligned  Access
       Control (UAC).

       The  uac  command  enables or disables the display of "Unaligned access" messages. The command sets or displays the UAC_NOPRINT, UAC_NOFIX,
       and UAC_SIGBUS options, as defined in setsysinfo(2).

       If value is not specified, the current option setting is displayed. You can specify value as either 0 (zero) or 1 (one).   If  value  is  0
       (zero), the option is turned on and messages are not displayed. If value is 1 (one), the option is turned off and messages are displayed.

       Keywords can be used singly, or in any combination.  However, the reset keyword overrides any other keywords it is used with.

RESTRICTIONS

       You must be superuser to set the system option.

EXAMPLES

       Both of the following commands disable messages for the parent process: # uac p 0

	      # uac p noprint Both of the following commands enable messages for the system: # uac s 1

	      #  uac  s  reset	The  following	command disables fixing of an unaligned access fault, disables printing a message for an unaligned
	      access fault to the parent process, and enables delivery of a SIGBUS signal to the parent process: # uac p nofix noprint sigbus

SEE ALSO

       getsysinfo(2), setsysinfo(2)

       Programmer's Guide

																	    uac(1)
All times are GMT -4. The time now is 09:29 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy